A semiconductor device such as, for example, a large scale integrated circuit (LSI) or a metal oxide semiconductor (MOS) transistor is manufactured by performing a processing such as, for example, doping, etching, chemical vapor deposition (CVD), or sputtering on a semiconductor substrate (wafer) which is a substrate to be processed.
Here, when doping is performed on the substrate, doping at a low concentration may be required. Japanese Patent Application Laid-Open No. 2004-128209 discloses a technology related to doping at a low concentration on the substrate.
In Japanese Patent Application Laid-Open No. 2004-128209, it is described that, in order to perform low concentration doping, it is required to lower a pressure within a vacuum container, and decrease a partial pressure of a doping gas. Further, in Japanese Patent Application Laid-Open No. 2004-128209, it is described that, when helium (He) that does not cause appreciable ion irradiation damage to a sample is used as a dilution gas, an electric discharge is hardly initiated at a low pressure. Japanese Patent Application Laid-Open No. 2004-128209 discloses a plasma doping method for solving these problems. The plasma doping method includes a first step of placing a sample on a sample electrode within a vacuum container, a second step of exhausting the inside of the vacuum container while supplying a gas into the vacuum container and generating plasma within the vacuum container by supplying a high frequency electrode to a plasma source while controlling the pressure inside of the vacuum container to a first pressure, and a third step of controlling the pressure inside of the vacuum container to a second pressure that is lower than the first pressure while the plasma is generated. In Japanese Patent Application Laid-Open No. 2004-128209, helium is used as a dilution gas and inductively-coupled plasma (ICP) is used as a plasma source.